A pharmacist has warned that five commonly prescribed medications — including antidepressants, antipsychotics and insulin — may interfere with your body’s ability to regulate temperature during a heatwave
11:42, 25 Jun 2026Updated 12:33, 26 Jun 2026
The heatwave is set to continue to the end of the week, with red and amber warnings for extreme heat across a swathe of England and Wales on Thursday(Image: Getty)
A health alert has been issued for people taking five different types of medication, as they could face harmful effects during the soaring temperatures.
A pharmacist has warned those on these drugs to exercise caution as the mercury rises this week, with Thursday expected to be the hottest day of the year so far.
The sweltering heatwave has led to “awful conditions” in hospitals, schools and nurseries are closed or operating early pick-up times or relaxing uniform rules, while train services have been disrupted.
South East Water has announced a temporary hosepipe ban for people living in Kent in the face of “high temperatures and record demand for water”.
On Wednesday, the June temperature record – held since the infamous summer of 1976 – was smashed as provisional figures suggest it reached 36.1C in Gosport, Hampshire.
The Met Office said on Thursday that the UK record for the highest June minimum temperature has also provisionally been broken, with temperatures only falling to 23.5C overnight at Bute Park, Cardiff.
The heatwave is set to continue to the end of the week, with red and amber warnings for extreme heat across a swathe of England and Wales on Thursday and amber warnings for parts of England on Friday and Saturday.
Dipa Kamdar, Senior Lecturer in Pharmacy Practice at Kingston University, explained on The Conversation website that: “The body uses several mechanisms to regulate temperature: sweating, blood flow to the skin and fluid balance. But some commonly prescribed drugs interfere with these processes, making it harder to stay cool.”
She reviewed a variety of medications commonly prescribed throughout the UK, emphasising the need for additional vigilance.
Antidepressants.
Ms Kamdar noted that two specific categories of antidepressants – selective serotonin reuptake inhibitors (SSRIs) and tricyclics (TCAs) – ‘may make summer harder to cope with’. She said: “They could even cause heat intolerance due to how they affect the body’s ability to sweat.”
Both these antidepressants are thought to work in part by influencing neurotransmitter levels in the brain – chiefly serotonin and noradrenaline.
This may result in certain patients perspiring less, which on a sweltering day, could make it harder for the body to cool itself down.
Ms Kamdar said: “Since sweating is a key cooling mechanism, any disruptions to this process can lead to heat-related illness. Excess sweating may also cause dehydration if fluids aren’t replaced.”
Antipsychotics.
Ms Kamdar explained: “Antipsychotics are used to treat psychosis, which can occur in schizophrenia and bipolar disorder. They do this by blocking the neurotransmitter dopamine – which in turn affects levels of the neurotransmitter serotonin. This can disrupt the hypothalamus’s ability to sense and respond to body temperature changes.
“As a consequence, someone taking an antipsychotic might not feel overheated or thirsty when it’s warm outside. This can result in low blood pressure and diminished heart function.
“The body then attempts to compensate by constricting the blood vessels and retaining heat. This consequently reduces perspiration and makes it more challenging to cool down effectively.”
Heart medications.
Beta-blockers reduce heart rate and decrease the force with which the heart pumps. However, Ms Kamdar warned that this can restrict blood flow to the skin – making it considerably more difficult for the body to dissipate heat during warmer weather.
She continued: “Diuretics are also commonly used in the treatment of high blood pressure or heart failure. But as these drugs increase urine output, this may lead to dehydration and electrolyte imbalances during hot weather.
“With less fluid available, the body may struggle to sweat properly. If you become severely dehydrated, you might actually stop feeling thirsty. Blood pressure can also drop, which may cause dizziness or fainting – especially when standing up.”
She also noted that ramipril and losartan, likewise prescribed for blood pressure management, can heighten the risk of dehydration. “These drugs block a system in the body that helps control blood pressure, fluid balance and thirst. This may reduce your natural urge to drink, increasing dehydration risk when it’s hot.”
Stimulants.
Much like amphetamines prescribed for ADHD, these substances affect numerous brain chemicals, including dopamine and noradrenaline. Such effects can elevate body temperature, speed up metabolism and interfere with the body’s ability to sweat, making it considerably harder to cool down, particularly during physical exertion or in warm conditions.
This could potentially result in dehydration, overheating, or even heatstroke. Stimulants may also mask feelings of exhaustion, causing people to push themselves too hard without realising the potential risk to their wellbeing.
Insulin.
Ms Kamdar outlined: “Warm temperatures cause the body’s blood vessels to dilate (widen) to aid in cooling off. However, this process results in faster absorption of insulin into the bloodstream due to increased blood flow to the area where insulin is injected – causing blood sugar levels to drop more rapidly.
“This can result in hypoglycaemia (low blood glucose level), potentially causing symptoms such as dizziness, shaking, sweating, irritability, and even loss of consciousness or seizures.
“Heat can also degrade insulin, reducing its effectiveness and making it unsafe. This is why insulin should be stored in the fridge until use – especially in summer. Damaged insulin will change appearance – turning cloudy or changing colour.”
To avoid heatstroke, Ms Kamdar suggests several preventative measures for those on common prescription drugs:Always check labels for storage instructions. Avoid leaving medications in hot places, such as in cars or on windowsills.Insulin isn’t the only drug affected by heat – inhalers and EpiPens can also malfunction or become less effective.Stay hydrated when it’s hot – unless your doctor has advised otherwise. Dehydration can actually worsen the effects of many medicines.For example, anti-inflammatory painkillers (such as ibuprofen) are more likely to cause kidney problems and bipolar medicines (including lithium) can become toxic if you’re dehydrated.Avoid peak heat hours and stay in cool environments when possible. Watch for warning signs of heat-related illness – such as dizziness, confusion, nausea or excessive sweating.Don’t stop taking your prescriptions medication without medical advice. If it’s affecting your ability to cope with the heat, speak with your doctor or pharmacist.
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